Method for forming castings



7 July 1', 1941.

H. F. HAGEMEYER METHOD FOR FORMING CASTINGS Original Filed Jan. 15, 19402 Sheets-Sheet -1 JicaezcZM @eweyer gi v a? 51% July 1 1941 H FHAGEMEYER METHOD FOR FORMING CASTINGS Original Filed Jan 15 1940 2Sheets-Sheet 2 Patented July 1, 1941.

METHOD FOR FORMING CASTING Henry F. Hagemeyer, Chicago, Ill., assignorto Castings Patent Corporation, Chicago, 11]., a corporation of IllinoisOriginal application January15, 1940, Serial No. 313,872. Divided andthis application April 6,

1940, Serial No. 328,214

7 Claims.

This invention relates generally to the art of formingcastings and ismore. particularly concerned with a novel method for forming castingswhich results in the production of castings having a uniform highquality and in which porosity, lack of uniformity, the formation andentrainment of'oxides and occluded gases, distortion, bad surfacefinish, and other well-known defects likely to be present in castingsare largely eliminated. The present application is a division of mycopending application Serial No. 313,872.

By casting processes as ordinarily practiced, several mold cavities areconnected to a runner by feeders and the runner is in turn connected toa sprue or filling opening. The fused metal .is then poured into thesprue and runs down the runner, through the feeders and into the moldcavities, or in the case of pressure castings is forced into the sprue.This rapid movement of the metal, together with the splashing andspraying about-of the metal within the mold, causes oxides formed at thesurface of the fused metal to be mixed with the metal and to be trappedtherein when the metal hardens. Also, during the process of pouring themolten metal into the mold, frequently quantities of gases and air aretrapped within the castings, thereby producing a spongy structure whichweakens the resulting casting and also causes the rejection of castingsthat are intended to be fluid tight, such, for instance, as engine orcompressor cylinder blocks and heads, valves, pipe fittings, and thelike.

Another disadvantage frequently encountered in ordinary castingprocesses is that the metal in the runner and sprue solidifies after themetal in the mold impressions. The subsequent shrinkage of the runner,therefore, puts considerable vide an improved method of molding thatprevents the cooling and attendant shrinking of the castings and runnerfrom causing distortions or strains in the castings. v

A still further object of the present invention is to provide a novelmethod for forming castings that allows the runner .to shrink away fromthe several castings as the runner cools without putting excessivestrains on the castings.

A still further object of the present invention is to provide a novelmethod that permits the casting of metal at lower temperatures thanthose stress on the castings, which frequently. results in the completedcastings having strains therein, or in the castings being distorted.

It is the principal object of the present invention to overcome theabove generally recognized defects in'castings.

A more specific object of the present invention is to form castings bycausing the fused metal to flow into and within a mold in a novel mannerthat minimizes the formation of oxides and gases and prevents theirocclusion, and that therefore gives the resulting casting a morehomogeneous structure and a more uniform density.

A further object of the present invention is to form castings in a novelmanner that prevents oxides formed at the surfaces of the fused metalfrom becoming entrained within the casting.

An additional objector my invention is to procustomarily used, and inwhich a definite but relatively low pressure is used to form theimpression of the mold.

Another object of my invention is to provide a casting process thatkeeps the oxide film on the molten metal fiowing into the mold inconstant I motion until it touches the mold surface andthereafterprevents the movement of any metal which has been brought into contactwith the mold surface.

An additional object is to provide a novel casting process that permitsthe use of much smaller sprues and runners than customarily used.

Other objects and advantages of the present invention will becomeapparent from the following description and accompanying drawings, in

which:

Fig. 1 isa plan view of several different types of castings shown joinedto a runner and appearing as they would just after the metal hassolidified. In the interest of clarity of illustration, the outline ofthe mold within which these castings were formed has been omitted;

Fig. 2 is an end elevationaL-view taken in the direction of the arrowsalong the line 2-2 of Fig. 1; I

Figs. 3, 4 5, 6, 7 and 8' may be considered as. sectional views taken inthe direction of the arrows, respectively, along thelines 3-4, 4-4, 55,6-6, 1-1, and 8-8 of Fig. 1. In these views, Figs. 3 to 8,. the portionsof the mold surrounding the respective sections are included in theviews.

In the drawings in which similar characters of reference refer tosimilar parts throughout the several views, the two mold halves, whichwill be referred to as the drag l0 and cope II, are preferably formed ofa gypsum base compound'in the manner as described in my copendingapplication 1 Serial No. 203,872, although it will beunderst'qpd thatthe method comprising the present invention is adapted for use withmolds composed of other the mold cavities wherever this becomesnecessary or advisable. The practice of using cores and other separatelyformed mold parts is well understood and will not be described here,inasmuch as this invention does not contemplate any change in the use ofthese mold elements.

The essence of the molding method comprising my invention is to causethe metal flowing into the mold to form a globule around the point ofentrance of the metal. This globule is then constantly and comparativelyslowly expanded by additional metal running into the inside thereof,

until the entire mold cavity is full. This I accomplish with as littleturbulence in the metal as possible, and thus oxides formed at thesurface of the globule remain on the surface and are not entrained inthe molten metal. As theglobule expands, these oxides are broughtagainst the surface of the mold cavity. whereupon the metal touching thewall becomes chilled somewhat and its viscosity thereby increased to apoint where it remains in place against the wall of the mold andimmobilizes the oxides, while the hotter and the surface film on theglobule is in constant controlled motion until it touches the mold walland thereafter cannot mix with the molten metal, nor can chunks ofthickened metal come loose from the walls and re-enter the still flowingmetal.

In order to promote the flow of metal in the mold in the manner as abovedescribed, I tilt the mold, so that the metal must run .uphill along thefeeders and in the casting impression, which it enters at its lowestpoint. Between the feeders and the mold cavity, a small orifice isprovided through which the metal must run. This orifice slows the rateof flow of the 'metal and allows the formation and gradual expansion ofa globule of metal within the mold cavity. Preferably the mold is soarranged that the metal flows into a casting impression at its lowestpoint, so'that the globule around the inlet open-.

ing is formed as quickly as possible and splashing of the metal withinthe mold is prevented, although practical considerations affecting thelayout of the mold may make it advisable to bring the metal into thecasting impressionslightly above, the lowest point. If the metal entersthe impression above the lowest point, it will be appreciated that aglobule may not form aroundthe inlet openingimmediately, but will beformed as soon as the level of the molten metal in the castingimpression rises to the level of the inlet opening. If the formation ofthis-globule does not take too long, no serious'effects .will be noticedin the casting produced, since the metal fiows slowly into theimpression and this forms a pool, the level of which quickly rises tocover the inlet opening without causing the metal to be scattered in theimpression.

It may be said that, as a rule, the mold should be laid out to bring themetal into the casting ,impression at the-lowest point, but if thisappears to be impractical, the metal should flow into the impression-asclose to its lowest point as can be arranged, so that the quality of thecastings will suffer as little as possible. It is also advisable tobring the metal into the impression at the thickest section of thecasting to be produced, so that the temperature of the metal reachingthe several portions of the casting impression will be more constant.

As will be explained more fully later, the metal is slowed in its fiowinto the casting impressions by a restriction placed in the path of flowof the metal rather than by having its rate of flow determined by theventing capacity of the mold. I prefer that the head behind the metalflowing into the mold should be sufiicient so that a pressure of abouttwo and one-half to three pounds per square inch will be brought to bearupon the metal at the top of the highest impression when the mold andsprue are full. It should be observed, however, that since the metalflows through a restriction before'it reaches the impression and flowsinto the impression at a rate slower than the venting rate of the mold,the pressure within the impression will be very low until the impressionis filled, whereupon the full head will immediately be brought into bearto form a sharp impression of the mold.

Since the metal is always caused to flow uphill, I form the majorportion of the impression in the cope. This is contrary to usual castingpractice, but works well with the present method. It is also usualcasting practice to place the portion of the casting requiring the bestfinish in the drag, but with the present process the finish produced byall portions of the impression are equally good.

-In the drawings, I have shown typical molded parts and the molds Iprefer to use in carrying out my process. As shown in Fig. 3, the copeI2 is placed upon the drag I0 and the plane of juncture of these twomold halves will be referred to as the parting line H. A runner cavityl6 extends substantially down the center of the mold and joins the spruel8 at one end thereof. This sprue extends upwardly through the cope andis further extended above the top of the mold by an asbestos papersleeve 20, the lower end of which sets in an annular slot 22 concentricwith the sprue opening in the top of the cope. The height of the sleeveshould be such that the hydrostatic head at the top of the highestcasting impression will be from about two and one-half to three poundswhen the sprue is reasonably full.

At intervals along the sides of the runner I6, branches or feeders 24extend outwardly therefrom. These feeders 24 usually lead to a generallycylindrical cavity which I call a shrink bob cavity 26 and from thesethe metal flows into the mold impression through a neck 21. The purposeof this shrink bob cavity is to provide a reservoir of metal thatsolidifies after the casting proper, and thus provides a quantity ofmetal which can be drawn into the casting when shrinkage in this elementtakes place. By the use of this shrink bob, I effectively prevent theformation of voids in the castings due to shrinkage of the metal. Itwill be appreciated that the casting will be removed from the mold withthe shrink bob attached thereto and that the shrink bob will ordinarilybe removed from the casting before the casting is used.

' Between the shrink bob 26 and the feeder 24, the metal is forced toflow through a very small orifice 28 which restricts the fiow of metalinto words, at right angles to the outlet of the shrink bob.

the'mold, while the interposition of the shrink bob between the orifice28 and the casting impression permits the fiow of metal to be slowedafter passing through the orifice, and before it reaches the castingimpression. Preferably-the orifice and outlet. of the shrink bob shouldnot be in a straight line as the jet action produced by the orificemight carry through and produce turbulence or spreading out of the metalin the casting impression. I, therefore, prefer-that the In Fig. 5,which illustrates parts I), d and f in section, it will be seen that themold is in general similar to that shown in Fig. 4. Since this partrequires less metal than that shown in Fig. 4, however, the shrink bob26, neck 21 and orifice 28 are all smaller than the similar parts inFig. 4. In forming this mold, the feeder 2|,

shrink bob 26 and neck 21 are all formed by cavities in the cope only,while the orifice is produced by a cavity in the drag, although it willbe appreciated that nothing in my process requires that these severalelements be specifically so formed.

Fig. 6 illustrates a ring gear requiring a comparatively small amount ofmetal. For this reason the shrink bob has been omitted. Since the thesurface of the mold cavity as the two streams of metal join.

It has been found thatif the part tobe cast is quite small, the shrinkbob may, in some instances, be dispensed with, in which event the feederis connected directly to the casting impression by the small orifice.Such an arrangement is shown in Figs. 6 and 8.

In arranging the mold, care should be taken to see that thecross-sectional areas of the one or more runners are considerablygreater thanthe total cross-sectional areas of the orifices leadingtherefrom, and that the cross-sectional area of the sprue is severaltimes greater than the total of the similar areas of the runnersattached thereto. This is done so that when the pouring operation isstarted, the sprue and then the runners will immediately fill and bringthe full hydrostatic head in the sprue to bear toforce the metal throughthe orifices. Since the runners and sprue are kept full during thepouring operation, the danger'of entraining oxides and gases is greatlylessened.

For convenience in discussing the several cast ings attached to therunner in Fig. 1, those castings below the runner are lettered from a toe beginning at the sprue, while those above the runner are similarlylettered from I to i. Of

these parts, those lettered a, c and e are alike and are alternatedalong the runner with parts I), d and I. These parts are positionedalong the runner much in the manner that I use for regularly producingcastings, while parts g,.h, i and :i are odd parts which are illustratedfor the purpose of better disclosing the present invention. The parts a,c and e, as may be seen from Fig. 4, are of. comparatively heavy'sectionand it is for this reason that a comparatively large shrink bob 2' isused. I

Although for practical considerations; I have not shown the metalas-running into the absolute bottom of the mold impression in Fig. 4. itwill be seen that when this mold is tilted into pouring position, asshown in Fig. 3, not much metal will need to flow into the impressionbefore a globule is formed. This globule can be expanded withoutbreaking, until the mold is full. The small orifice 28 through which themetal must run in passing from the feeder to the shrink bob is formed inthis instance by overlapping slots in the cope and drag, and thus theorifice causes metalfiowing therethrough-to flow vertically, or. inother bottom surface of this ring gear is flat and since its totalheight is well within the limits of the cope alone, this part is formedby a cavity in the cope only.

The rectangular part illustrated in Fig. 7 is of considerable height andfor this reason the bottom of the casting, together with the shrink bob26 and neck 21, are all formed in the cope, but ofiset downwardly wellbelow the normal parting line of the mold. As in the case of Fig. 5, theorifice is formed by a groove in the drag overlapping the cavities inthe cope. The metal is delivered from the feeder 24 to the orifice 28 bya downwardly extending feeder extension 24'.

In Fig. 8 is shown a beveled pinion that is small enough to require noshrink bob. In forming this part, mold cavities are formed in both thecope and drag, while the neck leading from the orifice to the principalimpression is wholly within the drag.-

The above illustrations are given merely for the purpose of showing theadaptability of the process for use in forming diiferenttypes ofcastings and should not be understood as limiting each of the particularparts to the particular mold arrangement shown. Each of the parts shown.in Figs. 4rto 8 is illustrated somewhat smaller than full scale.' Itwill be appreciated also that although I have shown a single runner inthe drawings, I intend that more runners may be used if desired andthat, if desired, ,a sprue of any suitable material of low heatconductivity may be used'in place of the asbestos paper sleeve shown.v

An additional utility of the small orifice 20,

I besides itscontrol over the rate of fiow of the metal into the molds,is that after the metal in the mold solidifies and the runner startscontracting, the metal will break or stretch across the thin section atthe orifice. That is, the interposition of this easily fractured piecebetween the molded pieces and the runner protects the molded pieces frombeing distorted by limiting the amount of pull to which the moldedpieces can be subjected to the amount of force which is necessarytostretch or break this small section. In carrying out this function ofthe orifice, I prefer that the smallest portion of the orifice should belocated contiguous to the body of metal which solidifies last.- Withthis arrangement, the separation of the castings from the runner. willordinarily occur while the metal at the orifice is still soft, and thusthe stress on the castings is at a minimum. To reduce the pull necessaryto bring about this separation even further, I prefer that the cornersof the orifice where it joins the larger body of metal should be sharpand not rounded, in order to give the section of metal at this point aslittle strength as possible. It has been found, for instance, that whena mold arrangement such as is shown in Fig. 1 is castand allowed to cooland the mold material is washed or broken away from the metal, all ofthe cast pieces will be found separated from the runner with theoccasional exception of parts close to the sprue, such for instance asthose in the positions a and ,f.

The size of the orifice 28 used depends in each instance upon theventing capacity of the mold and should as a maximum be of such sizethat the factor limiting the rate of flow of metal into the mold is thesize of the orifice rather than the venting capacity of the mold. Thesize of this.

orifice is not critical inasmuch as it may be considerably smaller thanthe maximum mentioned above. As a general rule, I have found that thecross-sectional area of the orifice should be ap proximately .0007square inch for each ounce of weight of the casting to be produced whenthe molds are constructed in the manner described in my copendingapplicationpreviously referred to and the alloy is of the fluidity ofyellow brass in the 60% copper-40% zinc group Alloys of higher viscositywill require somewhat larger orifices.

Many factors, such as the hydrostatic head used, alloy being cast,volume. of the mold; etc., influence the size of this orifice, but thefigure given will serve as a starting point from which 1. The method ofproducing metallic castings in a mold impression from fused metal whichcomprises manipulating the fused metal to form a globule in the moldimpression, said globule being held together by gravity and the surfacetension of the fused metal, continuously expanding the globule bygradually adding metal thereto at low velocity, the expansion of saidglobule being continued uninterruptedly until the mold impression isfilled, and the step of continuously adding metal to the globule toexpand the same being so conducted that disintegration of or turbulencein the globule is prevented.

2. The method of producing metallic castings in a porous mold impressionfrom fused metal which comprises manipulating the fused metal to form aglobule in the mold impression, said globule being held together by thesurface tension and gravity of the fused metal, continuously expandingthe globule by adding metal thereto at low velocity, the expansion ofsaid globule being continued uninterruptedly until the mold impressionis filled, and the step of continuously adding metal to the globule toexpand the same being conducted with substantially no turbulence, sothat disintegration of or turbulence in the globule is prevented, andmetal on the surface of said globule once having touched the surface ofsaid impression and having become chilled and thickened somewhatthereby, the continued expansion of said globule will not cause relativemovement between the surface of the impression and the surface of themetal in contact therewith.

3. The method of producing metallic castings in a mold impression fromfused metal which comprises manipulating the fused metal to form aglobule in the mold impression, said globule being held together bygravity and the surface tension of the fused metal, continuouslyexpanding the globule by gradually adding fused metal thereto at lowvelocity, the expansion of said globule be ing continued until the moldimpression is filled, the step of continuously adding metal to theglobule to expand the same being so conducted that disintegration of theglobule or turbulence therein is prevented, and the rate at which metalis added to the globule being less than the venting capacity of themold.

4. The method of producing metallic castings in a mold impression whichcomprises filling the mold impression from a runner impression,interposing a small orifice between the mold impression and runnerimpression to produce a weak section between the useful casting and therunner, and breaking the said weak section by mutual contraction of thecasting and runner to separate the useful casting from the runner beforethe runner and casting have completely cooled.

5. The method of producing metallic castings in a mold impression fromfused metal which comprises manipulating the fused metal to form aglobule in the mold-impression, said globule being ,held together bygravity and the surface tension of the fused metal, continuouslyexpanding the globule by gradually adding fused metal thereto at lowvelocity, the metal flowing to said globule being under a substantialhead, but being restricted in entering the mold impression by a smallorifice so that the flow into said mold will be at a rate slower thanthe venting capacity of the mold, whereby the metal in said moldimpression will be surrounded by air at substantially atmosphericpressure while the mold is filling, but

, will be subjected to the full head of the metal to form a sharpimpression immediately the mold and the whole being so conducted thatthe metal flows substantially continuously uphill to the castingimpression and flows substantially continuously uphill within thecasting impression.

7. The method of producing metallic castings in a mold impression whichcomprises filling the mold impression from a runner impression, interposing a restriction between the mold impression and the runnerimpression to reduce the rate of flow of the metal, introducing anenlargement between the restriction and the mold impression to permitthe flowing metal to become quiet before flowing into the castingimpression, and the whole being so conducted that the metal flowssubstantially continuously uphill to the casting impression and flowssubstantially continuously uphill within the casting impression, saidcasting impression being filled with metal at a temperature notsubstantially higher than 200 F. above its temperature of fusion.

HENRY F. HAGEMEYER.

